Chemotherapy-induced diarrhoea: what you need to know

Do not wait for severe symptoms before reporting frequent or watery stools. Your team may need to check the cause, review your medicines, and recommend a suitable anti-diarrhoeal treatment.

Some chemotherapy medicines irritate the rapidly renewing lining of the bowel, so stools may become loose or more frequent. Infection, antibiotics, other medicines, diet changes, or the cancer itself can also contribute. Because the right response depends on the cause, tell your team when the change began, how often you are passing stool, and whether there is pain, fever, or blood.

Follow the contact instructions supplied by your oncology service. Sip fluids regularly and choose drinks your team has approved; an oral rehydration solution may help replace salts as well as water. Keep a record of bowel movements and associated symptoms. Eat small, plain meals if you can, and avoid foods or drinks that clearly worsen the diarrhoea.

Only take anti-diarrhoeal medicine after checking the plan provided by your cancer team. A product that is appropriate for treatment-related irritation may be unsuitable when infection or bowel inflammation is suspected. Do not stop chemotherapy or change prescribed doses on your own.

Contact your cancer team urgently for fever or chills, blood or black stool, severe or increasing abdominal pain, a swollen abdomen, repeated vomiting, inability to keep fluids down, marked weakness, dizziness, confusion, very little urine, or rapidly worsening diarrhoea. Use the emergency service recommended by your oncology unit if you cannot reach the team or feel seriously unwell.

Ask which bowel changes should trigger a same-day call, whether you should keep oral rehydration solution or an anti-diarrhoeal medicine at home, and whether any current medicines could worsen symptoms. Confirm whom to contact outside clinic hours and whether your next treatment needs reassessment after an episode.